I like this idea as well, I have been using Sync for a while and love the simpliciy of it... just wish I had more control over who I send the keys to as I have noticed some friends reply and CC other people into the email with the sync key. I installed syncthings this weekend to have a look at the diffrence. syncthings has the idea of nodes and repositories... so you set up trusted nodes with two keys.... meaning you set up one node and send your friend a key, he/she has to set up the node on there side with your public key and then send you a public key of their own... so its a two way trusted node.... then when you want to sync a repository with them you simply check a box to "sync" with their node. I for one like BTSync more as it just is a slicker and nicer interface and easier to set up... but I would love to see a better implementation of the key trust.
